I'm trying to modify the ListProperty "Sapphire.Add" action to immediately call the "Sapphire.Browse" action. So far I have filtered out the "Sapphire.Add" event and replaced with my own custom ActionHandler. I would like to now call "Sapphire.Add" and Sapphire.Browse in my action handler. Is this possible?

You will not be able to call "Sapphire.Add" from your action handler since you've filtered it out, so it "doesn't exist" in your context, but its implementation is quite simple. You just need to call insert on the list.